1. Field of the Invention
The present invention relates to a display apparatus and a display method suitable for use in, for example, a liquid crystal display device.
2. Description of the Related Art
In display apparatuses, for example, liquid crystal display devices, since pixels of a liquid crystal panel do not emit light by themselves, a backlight is disposed on the back surface of the liquid crystal panel to illuminate the back surface of the liquid crystal panel. Thus, an image can be displayed.
In known liquid crystal display devices, the backlight illuminates the entire display screen of a liquid crystal panel at a uniform intensity. By controlling the aperture ratio of each pixel of the liquid crystal panel to adjust the shielding of light emitted from the backlight, each portion of the display screen receives necessary luminance of light. Accordingly, for example, even when the entire display screen is dark, the backlight emits light substantially at its maximum intensity. This unnecessarily illuminating backlight increases the power consumption of a liquid crystal display device, which is a problem.
To solve such a problem of a liquid crystal display device having a backlight, for example, a method has been proposed for controlling the luminance of the entire backlight on the basis of display luminance information of the entire display screen.
Additionally, a method has been proposed for dividing the display screen into a plurality of regions in accordance with light sources of a backlight and individually controlling the luminance of the light sources in accordance with the required luminance for each divided region (refer to, for example, Japanese Unexamined Patent Application Publication No. 2004-212503).
As used herein, the term “emission luminance” refers to the luminance of light when the light is being emitted from a light source. The term “display luminance” refers to the luminance of light emitted from the light source when the light is passing through a display unit (display screen). This same definition is used throughout this specification.
FIGS. 18A and 18B schematically illustrate such a control method. For example, as shown in FIG. 18A, an image (original image) includes a dark elliptical portion substantially at the center of the image, and the image becomes progressively brighter towards the periphery thereof. A backlight c of a liquid crystal display device that displays this image includes a plurality of vertically and horizontally divided light sources d, d, d, . . . , as shown in FIG. 18B. To display the image shown in FIG. 18A, the two light sources d and d corresponding to the portion having the lowest display luminance are controlled to decrease the emission luminance.
By displaying an image while partially controlling the emission luminance of the backlight c, the unnecessary backlight emission is prevented, and therefore, the power consumption can be reduced.